The present application is based on Japanese Patent Applications No. 2001-265422, 2001-265423 and 2001-265424, which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a light-emitting diode lamp (hereinafter referred to as xe2x80x9cLED lampxe2x80x9d) in which a single light-emitting element or a plurality of light-emitting elements, and leads and wires electrically connected to the single or plurality of light-emitting element(s) are packed in a package such as a synthetic resin package and sealed with a light-transmissive material such as a transparent epoxy resin. Incidentally, in this specification, an LED chip itself is called xe2x80x9clight-emitting elementxe2x80x9d whereas a light-emitting device having a plurality of LED chips mounted therein is collectively called xe2x80x9clight-emitting diode lampxe2x80x9d or xe2x80x9cLED lampxe2x80x9d, further, more comprehensively called xe2x80x9cLED devicexe2x80x9d. A lead frame as a raw material thereof is called xe2x80x9cLED lead framexe2x80x9d.
2. Description of the Related Art
A surface mounting chip LED (SMD) type LED lamp has been heretofore used in a light source for a backlight unit, or the like. In the SMD type LED lamp, a plurality of metal leads disposed in an injection-molded synthetic resin package, and a plurality of light emitting elements mounted on one of the leads and electrically connected to the other leads by wire-bonding are entirely sealed with a transparent epoxy resin or the like.
In the LED lamp having such a plurality of light-emitting elements, however, luminous intensity distribution characteristic varies in accordance with the respective light-emitting elements. Moreover, heat-radiating characteristic is worsened compared with that of a package of a single light-emitting element. Hence, the respective light-emitting elements become uneven both in heat-radiating characteristic and in light-emitting efficiency. In addition, there arises a problem that color-mixing characteristic is worsened when a plurality of light-emitting elements different in wavelength are mounted in the LED lamp.
Further, in this LED lamp, however, lead portions (LED leads) by which the lamp is bonded on the mount board via solder is made flat. The viscosity of solder is reduced instantaneously when the LED lamp is made to pass through a reflow furnace at a high temperature in order to solder the LED lamp onto the mount board. For this reason, surface tension of solder is applied on the lead portions but the LED lamp is hardly positioned because the lead portions are so flat that the LED lamp slides. For this reason, in the LED lamp having such leads bent once, there is a problem that accurate mounting can be hardly made.
Still further, an example of a related-art LED lead frame for the LED lamp will be described with reference to FIG. 7. FIG. 7 is a plan view showing the configuration of the related art LED lead frame.
As shown in FIG. 7, in the LED lead frame 21, four electrically conductive leads 25a, 25b, 25c and 25d are protruded inward from an outer frame 23 so that an injection-molded synthetic resin package 22 is fixed to tips of the leads. A plurality of light-emitting elements are mounted in the package 22, electrically connected to the LED lead frame 21 by wire-bonding and then sealed with a sealing resin. Thus, a body portion of an LED lamp is produced. Then, the electrically conductive leads 25a, 25b, 25c and 25d are cut into a predetermined length and then bent along the outer circumference of the package 22. Thus, a surface-mountable LED lamp is obtained.
In the LED lead frame 21, however, nothing supports the package 22 after the electrically conductive leads 25a, . . . , and 25d are cut. Therefore, the package 22 must be fixed by a jig or something when the electrically conductive leads 25a, . . . , and 25d are to be bent back or forth along the outer circumference of the package 22. For this reason, there is fear that the package 22 may be broken. Moreover, the electrically conductive leads 25a, . . . , and 25d cannot be bent accurately because the package 22 cannot be fixed firmly. Hence, there is a problem that inconsistency in positioning accuracy with respect to a partner member may occur in a post-process.
Therefore, an object of the present invention is to provide an SMD type LED device in which uniformity of luminous intensity distribution characteristic in respective light-emitting elements and improvement both in heat radiating characteristic and in color-mixing characteristic can be achieved.
Another object of the present invention is to provide an LED device which can be positioned stably without sliding of the LED device when soldered onto a mount board and which can be mounted on the mount board accurately.
Still another object of the present invention is to provide a method for manufacturing an LED device lead frame in which electrically conductive leads can be bent with stable accuracy while a package is fixed firmly without being damaged in a process of bending the electrically conductive leads, and an LED device lead frame used for manufacturing the LED device.
(1) According to the invention, there is provided an LED device having: a plurality of light-emitting elements sealed with a light-transmissive material in a package, wherein: the plurality of light-emitting elements are arranged in a single row in the inside of an opening portion of the package and in order of element height so that a light-emitting element higher in element height is disposed on an outer side of the single row; and the inside of the opening portion of the package is sealed with the light-transmissive material.
The light-transmissive material for sealing the inside of the opening portion of the package is shrunk when cured from a liquid state. For this reason, the surface of the light-transmissive material in the center portion of the package is dented so that the outer side of the package becomes higher than the center portion. Accordingly, when the plurality of light-emitting elements are arranged in such order of element height that a light-emitting element higher in element height is disposed on an outer side of the single row, distances from light emitting surfaces of the respective light-emitting elements to the surface of the light-transmissive material are made uniform, so that luminous intensity distribution characteristic is made uniform.
In this manner, in the LED device having a plurality of light-emitting elements sealed with a light-transmissive material in a package, luminous intensity distribution characteristic can be improved.
(2) According to the invention, in the LED device having the configuration defined in (1), one sheet of electrically conductive lead for mounting the plurality of light-emitting elements protrudes out of the package to thereby form a protrusion provided in a center portion of the package.
With such a configuration, distances from the respective light-emitting elements to a heat-radiating portion are made uniform, so that heat radiation is made uniform. Accordingly, light-emitting efficiency is made uniform, so that the LED device can be provided as an excellent LED device.
(3) According to the invention, in the LED device having the configuration defined in (1) or (2), the opening portion has its periphery constituted by slopes provided in a lengthwise direction of the package and slopes provided in a widthwise direction of the package, and the slopes provided in the lengthwise direction are different in inclination from the slopes provided in the widthwise direction so that the inclination of the slopes provided in the widthwise direction is gentler.
With such a configuration, the opening portion is formed so that light is not diffused in the lengthwise direction but light is diffused in the widthwise direction. Hence, it is easy to guide light into a thin light guide plate. This contributes to increase in luminance of a backlight unit. In addition, when a plurality of such LED devices are used, color mixing characteristic of adjacent LED devices is improved.
(4) According to the invention, in the LED device having the configuration defined in any one of (1) through (3), the plurality of light-emitting elements are different in wavelength of emitted light and are arranged in a single row at intervals of a narrow pitch.
With such a configuration, color-mixing characteristic of the light-emitting elements is improved in all wavelengths of emitted light, so that good color-mixing characteristic is obtained when light in full color is emitted from the LED device.
(5) According to the invention, in the LED device having the configuration defined in any one of (1) through (4), the plurality of light-emitting elements include at least one red light emitting element, at least one green light-emitting element, and at least one blue light-emitting element.
In this manner, when the LED device is constituted by three color types of light emitting elements for emitting light in red, green and blue which are light""s three primary colors, the LED device can be used as a light source for a backlight unit because white light is emitted from the LED device. In addition, because the opening portion is formed so that light is diffused in the widthwise direction, it is easy to guide light into a thin light guide plate. Hence, the LED device contributes to increase in luminance of a backlight unit.
(6) According to the invention, in the LED device having the configuration defined in any one of (1) through (5), the plurality of light-emitting elements include two red light-emitting elements disposed on outer sides respectively, two blue light-emitting elements disposed on inner sides of the two red light-emitting elements respectively, and one green light-emitting element disposed in a center of the single row.
Each of a red light-emitting element and a blue light-emitting element is lower in luminance than a green light-emitting element. Hence, when two red light-emitting elements and two blue-light-emitting elements are used, the three colors are balanced to obtain white light emission in a state of uniform heat load balance. Moreover, because a blue light-emitting element is superior in light-emitting efficiency to a green light-emitting element, the LED device is suitable for the purpose of requiring bluish white light or for the purpose of requiring electric power saving. In addition, a red light-emitting element is higher in element height than each of a green light-emitting element and a blue-light-emitting element. Hence, when the red light-emitting elements are disposed on outermost sides respectively, distances from light-emitting surfaces of the respective light-emitting elements to the surface of the sealing material dented in the center portion are made uniform, and luminous intensity distribution characteristic is improved.
(7) According to the invention, there is provided an LED device having: a package; a plurality of leads; a plurality of light-emitting elements electrically connected to the plurality of leads; and a light-transmissive material with which the plurality of leads and the plurality of light-emitting elements are sealed in the package; wherein: protrusions of the plurality of leads pulled down out of the package are bent back and forth and/or left and right along a lower surface of the package; and tips of the plurality of bent leads are further bent up along side surfaces of the package.
Hence, when the LED device is soldered onto a mount board, solder is deposited even on the tips of the leads bent up along the side surfaces of the package. Surface tension of solder is balanced on the front and rear or left and right of the package while the skirts of solder are widened. Hence, the LED device can be mounted in a predetermined position while prevented from sliding.
In this manner, because the leads are bent up, that is, bent twice, surface tension of solder is balanced on the front and rear or left and right of the package while the skirts of solder are widened. Hence, the positioning accuracy of the LED device is improved, so that the LED device can be mounted accurately.
(8) According to the invention, in the LED device having the configuration defined in (7), protrusions of the plurality of leads are bent back and forth along a lower surface of the package, and tips of the plurality of bent leads are further bent up along side surfaces of the package.
In this manner, because the direction of bending of the leads is limited to a back-and forth direction, solder can be deposited on the package along the lengthwise direction of the package when the LED device is mounted. Hence, the length on which surface tension of the solder is applied is elongated so that more strongly balanced force is applied on the LED device. As a result, the LED device can be positioned more accurately when mounted.
(9) According to the invention, there is provided an LED lead frame for producing an LED device having a single light-emitting element or a plurality of light-emitting elements sealed with a light-transmissive material in a package, having: a plurality of electrically conductive leads for mounting the single light-emitting element or the plurality of light-emitting elements packed in the package, the plurality of electrically conductive leads being protruded out from one side of the package and connected to an outer frame of the LED lead frame; and a plurality of hanger leads protruded out from three sides of the package other than the one side of the package and connected to the other frame.
In the LED lead frame configured as described above, even after the electrically conductive leads are cut into a predetermined length, the package is fixed to the outer frame by the hanger leads extended in other three directions. Accordingly, also in a process of bending back or forth the electrically conductive leads along the package, the electrically conductive leads can be bent accurately without tottering because the package is fixed firmly. Moreover, because the package is fixed to the outer frame by the hanger leads extended in three directions, it is unnecessary to press the package so long as the outer frame is fixed firmly. Hence, there is no fear that the package may be broken. Incidentally, after the process of bending the electrically conductive leads is completed, the hanger leads which have become unnecessary may be preferably removed.
In this manner, the LED lead frame is provided as an LED lead frame in which the electrically conductive leads can be bent with stable accuracy while the package is fixed firmly without being damaged in the process of bending the electrically conductive leads.
(10) According to the invention, in the LED lead frame having the configuration defined in (9), ones of the plurality of hanger leads are provided in a direction of a side which is among the three sides of the package and opposite to the one side of the package.
In this manner, because a plurality of hanger leads are provided in a direction of a side opposite to the one side of the package, that is, in a direction opposite to the pulling-out direction of the electrically conductive leads, the package can be surely prevented from warping when the electrically conductive leads are bent back or forth along the package in the process of bending the electrically conductive leads. Hence, the electrically conductive leads can be bent more surely with stable accuracy.
(11) According to the invention, in the LED lead frame having the configuration defined in (9) or (10), the ones of the plurality of hanger leads provided in the direction of the side which is among the three sides of the package and opposite to the one side of the package are wide.
In this manner, because each of the hanger leads provided in a direction of a side opposite to the one side of the package, that is, in a direction opposite to the pulling-out direction of the electrically conductive leads is made wide, stiffness becomes large. Hence, the package can be surely prevented from warping when the electrically conductive leads are bent back or forth along the package in the process of bending the electrically conductive leads. Hence, the electrically conductive leads can be bent more surely with stable accuracy.
(12) According to the invention, in the LED lead frame having the configuration defined in any one of (9) through (11), ones of the plurality of hanger leads provided in directions of two sides among the three sides of the package and substantially perpendicular to the plurality of electrically conductive leads are wide.
In this manner, because each of the hanger leads provided in two directions substantially perpendicular to the plurality of electrically conductive leads is made wide, stiffness against warping force in the widthwise direction becomes large. Hence, the package can be surely prevented from warping when the electrically conductive leads are bent back or forth along the package in the process of bending the electrically conductive leads. Hence, the electrically conductive leads can be bent more surely with stable accuracy.
Further, using the LED lead frame according to any one of (9) to (12), an LED device described in any one of (1) to (8) or any other type of devices may be manufactured. The LED lead frame has at least one electrically conductive lead connected to one side of an outer frame of said LED lead frame, and a plurality of hanger leads protruded out toward and connected to three sides of said outer frame different from said one side to which said electrically conductive lead is connected. Next, at least one light-emitting element is mounted on said electrically conductive lead. Further, the light-emitting element is sealed with a light-transmissive material to form a package containing the light-emitting element such that a part of said electrically conductive lead is protruded out from said one side of said package and connected to said outer frame. The electrically conductive lead is separated from said outer frame. Thereafter, the electrically conductive lead is folded. In the case where a plurality of electrically conductive leads are formed in the LED lead frame, adjacent leads are folded different in thickness direction of the LED lead frame.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.